Great for presentations, job sites, home use and more, this 3-function pen includes a laser, flashlight and pen. The lights can be used together or separately for a wide variety of uses. The black ball-point pen features ultra-smooth tracking and retracts for safe, easy storage. 3 electric AG 13 cell batteries (LR44 or equivalent) are needed to operate laser (included). To insert, disassemble the pen as shown in diagram, following the correct battery polarity.